An agricultural row crop planter is a machine built for precisely distributing seed into the ground. The row crop planter generally includes a horizontal toolbar fixed to a hitch assembly for towing behind a tractor. Row units are mounted to the toolbar. In different configurations, seed may be stored at individual hoppers on each row unit, or it may be maintained in a central hopper and delivered to the row units on an as needed basis. The row units include ground-working tools for opening and closing a seed furrow, and a seed metering system for distributing seed to the seed furrow.
In its most basic form, the seed meter includes a housing and a seed disc. The housing is constructed such that it creates a reservoir to hold a seed pool. The seed pool may also be in a separate structure. The seed disc resides within the housing and rotates about a generally horizontal central axis. As the seed disc rotates, it passes through the seed pool where it picks up individual seeds. The seeds are subsequently dispensed into a seed chute where they drop into the seed furrow.
Early seed meters were comprised of mechanical means of singulating seeds. These meters were constructed such that fingers on the face of the seed disc gripped seeds as they passed through the seed pool, subsequently releasing those seeds as they passed over the seed chute. Although these mechanical seed meters are effective, they are limited in their ability to assure singulation of seeds and are prone to dispensing duplicates (i.e., multiple seeds) and/or failing to dispense at all (i.e., skips or misses). Other mechanical meters use cells in conjunction with brushes to trap seeds within the cavity and release them over the seed chute.
Systems that are more recent include an air seed meter, e.g., vacuum or positive pressure meters, wherein the mechanical fingers have been replaced by a disc with apertures. A pressure differential is formed across opposite sides of the seed disc, which generates a suction force at the seed cell apertures. As unobstructed seed cells pass through the seed pool, seeds are drawn onto or against the seed cells and remain thereon until the seed cell passes through a region of the housing with a reduced pressure differential. To create this reduced pressure differential region, generally the “vacuum” (i.e., lower pressure) side of the seed disc is exposed to air pressure near, but not always at, atmospheric levels.
At this point, seeds are released from the seed cell of the seed disc and into the seed chute. Compared to mechanical meters, air seed meters promote improved singulation across a wider range of speeds. A problem that exists with an air seed meter is that it can be difficult for the suction (negative) force or positive air force of the seed cell to draw or push seeds from a stagnant seed pool. Another problem with air seed meters, and specifically the seed disc, is that seeds not released at or near the edge of the seed disc are susceptible to increased ricochet or bounce, thereby negatively impacting seed spacing. For those air seed meters that do release seeds from at or near edge of the seed disc, seeds are sometimes knocked free of the cells on the seed disc by the seed meter housing sidewall because of the close proximity of the housing sidewall to the cell.
Furthermore, the fluid source, which may be a positive air source or a vacuum source, is generally a large device that supplies the air or vacuum pressure to multiple, if not all, of the row units of a planter. This requires a large pressure source, as well as a large number of hoses extending from the pressure source(s) and the row units. This creates clutter on the planter, which increases with the number of row units and/or seed meters on a planter. In addition, due to the sometimes long distances between the pressure source and the row unit, as well as the current state of and inefficiency of fans and vacuum distribution on planters, there may be a pressure drop, which can affect the efficiency of the fluid pressure at the row unit. To account for this drop, the pressure may need to be higher at the source, which requires more power as well.
Therefore, there is a need in the art for a row unit of a planter that includes an electric, integrated air pressure source at a row unit for providing a positive or negative pressure for the one or more seed meters of the row unit. The pressure source can include an electric motor and pressure generator on and/or integral to the row unit and/or seed meter.